all of the sudden i can't link to external sites

I went to add a link to an external site within the context of my blog but instead of going to http://www.website.com it’s going to http://www.mysite.com/postname/www.website.com. This goes to a page saying “whoops! whatever you are looking for cannot be found”. I haven’t made any changes to the site recently that I can think of. I tried linking to different urls and still getting the same problem.

I am creating the link by writing text in my blog post, highlighting the text I want to be the title of the link, clicking the insert/edit link button in the editor, and entering the url of the link there. Set to open in new window.

The existing links to external sites have not been affected. I can create links to pages within my site with no problem.

Everything was fine until today… haven’t touched the site in several days. What might be the problem here?